Functional analysis of the Rab1-COPII interaction.

SLAVIN ILEANA, MONETTA PABLO, ROMERO NAHUEL AND ALVAREZ CECILIA

Mar del Plata. Argentina

Congreso; SAIB; 2007

SAIB

FUNCTIONAL ANALYSIS OF THE RAB1-COPII INTERACTION Slavin I, MonettaP, RomeroN, Alvarez C. CIBICI-CONICET, Facultad Cs. Químicas, U.N.C. Export from the Endoplasmic Reticulum (ER) defines the first step of the secretory pathway and is mediated by the recruitment of the COPII coat complex (composed by Sar1p, sec23/24 and sec13/31). In the ER exit sites (ERES), COPII modulates sorting and concentration of cargo in COPII vesicles. Moreover, COPII assembly is up-regulated by increased levels of cargo proteins. After vesicle budding, COPII is exchanged by COPI complex, a crucial step for ER-Golgi transport. Rab1 GTPase acts as an essential component required for this transport by modulating COPI recruitment in ERES.We have previously shown that Rab1 interacts with Sec23. Here, we aim to explore the role of the Rab1-COPII interaction. We show that Rab1 also interacts with Sec23. Interestingly, depletion of Rab1 by expressing the Rab1 dominant negative mutant (Rab1N121I) or by iRNA, strongly suggests that COPII recruitment is Rab1 independent. However, the number of small COPII structures is markedly increased in Rab1 depleted cells, supporting our previous data showing that Rab1 modulated COPII dynamics. Furthermore, Rab1 knock down inhibits sorting of a Golgi cargo protein (GFP-GalT2) into the ERES. Taken together, our results strongly suggest that Rab1-COPII interaction is implicated in modulating COPII membrane association dynamics and cargo sorting into the ERES.